The present invention relates to a waveform data generating system using a waveform memory which stores the waveform data to determine a timbre of a musical tone.
In a known waveform data generating system, for performing a musical piece, waveform data is read out from a waveform memory assembled into an electronic musical instrument. A waveform of a musical tone with a pitch corresponding to a performance key operated is controlled by the read out waveform data. An example of such method is disclosed in U.S. Pat. No. 3,515,792. In this patent, an access speed to the waveform memory, which is sequentially performed from address 0 to the subsequent ones, is changeable according to a pitch of a musical tone. Therefore, the same timbre must be kept even if the pitch is changed. Nevertheless, a low-pitched tone and a high-pitched tone are equal to each other in the contents of the overtones, because the number of steps of reading out the waveform data from the waveform memory is fixed irrespective of pitches of a musical tone. Therefore, the timbre of a musical tone particularly in low-pitched tones is unsatisfactory. This problem may be solved with an additional provision of a plurality of external filters which are selectively used according to a range of the tone pitches. This approach, however, is accompanied by complicated construction and high cost to manufacture.